It is known in the art of microprocessor devices to provide a programmable control function. Such programmable microprocessor devices are employed in electronic thermostats. The typical electronic thermostat permits the user to enter a program of a set of desired temperatures for particular times of a repetitive time period such as a day or a week. Once this time/temperature program is entered the electronic thermostat controls the heater and/or the air conditioner to achieve the desired temperature at the desired time.
The typical electronic thermostat employs a keyboard of one or more momentary contact push buttons as an input device and a liquid crystal display as an output device. In accordance with the prior art the user operates the keys of the keyboard to input the program of desired temperatures for desired times and receives feedback regarding the program specification process via the liquid crystal display. In accordance with the typical prior art electronic thermostat the user enters a digital representation of the desired time and the desired temperature via a keyboard with the ten digits 0-9. The display will show the entered quantity also in digital form. Typically the operator is also permitted to review the time/temperature program stored in the electronic thermostat via the liquid crystal display by proper manipulation of the keyboard.
This technique known in the prior art is not without problems. Firstly, such electronic thermostats are often used by persons unsophisticated in the computer arts and therefore not familiar with the process of program entry. Most people are more familiar with analog representations of time and temperature than with the digital representations required by the prior art. Thus the type of input required and the type of output provided may be confusing to the user. Secondly, the provision of a keyboard and a liquid crystal display in such an electronic thermostat is an added expense that should be avoided if possible.
Thus it would be advantageous to be able to provide a technique for specification of a program of desired control states at desired times which provides analog representation of time input, which permits review of the program and which is less expensive in manufacture than the typical keyboard and LCD combination of the prior art.